Field of the Invention
The present invention relates to a rotary knob which is provided on an operation portion of an electronic device or the like and which is to be turned in a state in which the rotary knob is fitted on a rotation shaft.
Description of the Related Art
Rotary knobs are used for electronic devices such as mixing consoles to adjust volumes, for example. Such a rotary knob is constructed to be turnable in a state in which a rotation shaft is fitted in a mating hole, and is constructed to be removable from and mountable on the rotation shaft for repair, for example. Thus, the rotary knob needs an appropriate removal force which is required for the rotary knob to be removed from the rotation shaft. Accordingly, the rotary knob is preferably constructed such that a surface defining the mating hole into which the rotation shaft is to be inserted is in contact with the rotation shaft and such that the mating hole can absorb an error in the diameter of the rotation shaft.
For example, Patent Document 1 (Japanese Patent Application Publication No. 10-111373) discloses a rotary knob in which a mating portion to be fitted on a rotation shaft is constituted by a plurality of mating pieces defining a plurality of slits, and each of the mating pieces is connected to an outer wall member (outer circumferential member) of the rotary knob by an elastically deformable rib. This construction can provide an appropriate removal force and absorb an error in the diameter of the rotation shaft when the rotary knob is fitted on the rotation shaft. However, the mating portion and the outer wall member are shaped like a double-ply tube, resulting in increase in diameter of the rotary knob.
In small rotary knobs, in general, an outer wall member in most cases also serves as a mating portion due to physical limitation of size, making it difficult for the rotary knob to have the above-described construction.
As the rotary knob in which the mating portion is constituted by the outer wall member, Patent Document 2 (Japanese Unexamined Utility Model Application Publication No. 6-079039) discloses a rotary knob, for example. This rotary knob has a mating hole in which a rotation shaft including a cutout portion having a D-shape in cross section is to be fitted. Provided on an inner circumferential surface of the mating hole are a plurality of projections and an elastic portion to be engaged with a portion of the rotation shaft which is formed by the cutout portion. The projections and the elastic portion of the mating hole support the portion of the rotation shaft which is formed by the cutout portion, to stabilize a removal force.